Not Applicable
Not Applicable
The present invention relates to medical device delivery systems, particularly dilation balloon catheters employed in applications such as percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasty (PTCA) procedures, and more particularly to the utilization of a catheter having multiple inflation balloons for the delivery of medical devices, namely stents.
Balloon catheters, are a highly developed and well known field of medical technology. Balloon catheters are typically used to occlude and seal bodily spaces, expand blood vessels, and deliver a variety of medical devices.
Stents are medical devices that are commonly placed into a body vessel by way of a balloon catheter delivery system. A stent is a prosthesis which is generally tubular and which is expanded radially in a vessel or lumen to maintain its patency. Stents are widely used in body vessels, body canals, ducts or other body lumens.
In many stent delivery applications, the stent is often designed to be self-expanding. When these self-expanding stents are utilized, balloon catheters are typically designed to mount the stent upon the deflated balloon and further surround the stent with a retractable sheath. To actually deliver the stent the sheath is retracted thereby allowing the stent to expand away from the balloon. The balloon is then inflated to seat the stent in place. Stent delivery catheters which utilize a single balloon and a sheath can be seen in U.S. Pat. No. 5,192,297 to Hull, U.S. Pat. No. 5,360,401 to Turnland et al. and U.S. Pat. No. 5,453,090 to Martinez et al.
In the case of a non-self expanding stent, to deploy the stent the catheter must have a means to initially expand the stent from about the catheter and into the target vessel. Typically a balloon is inflated to expand the stent a sufficient diameter about the catheter and then deflated to release the stent. Subsequent to expanding the stent, in many applications the catheter must be completely removed to replace this first balloon with a second balloon more suitable for seating the stent in place, or alternatively an entirely new balloon catheter is used to seat the stent.
In some other applications the laborious and time consuming task of balloon or catheter changeover is avoided by utilizing a catheter which has multiple balloons mounted adjacently to one another. In these applications after an initial balloon expands the stent, the catheter is moved forward in the vessel to put the seating balloon into position under the now expanded stent. While these systems save time by avoiding the extra step of removing the catheter and replacing the balloon, they remain less than ideal as often the balloons are easily ruptured by the edges of the stent and the effect of the entire catheter being moved back and forth in the vessel, in order to properly position the stent, places additional unwanted friction and stress upon the vessel walls.
In many operations which utilize stents, the stent and catheter must often pass through a variety of interferences such as a build up of arterial plaque, hardened calcified legions, or other known medical conditions. The typical low pressure balloon used to expand the stent lacks the required strength, pressure, diameter and compliance characteristics to properly inflate the balloon through these anomalies without risk of rupture or vessel damage. As a result numerous catheter configurations have been developed to address the problems associated with these conditions.
U.S. Pat. No. 5,810,871 to Tuckey et al. discloses a stent delivery system which addresses the stent mounting and balloon puncture problems associated with previous catheters such as those described above, by providing an expandable sheath to be placed between the balloon and stent. Moreover, to protect the vessel from possible tearing as the stent is moved therethrough, the Tuckey catheter employs two end caps which contain the ends of the stent while the stent is compressed prior to expansion. Although Tuckey addresses some of the problems as stated above, Tuckey fails to provide a balloon with compliance, pressure and diameter characteristics for proper seating of the stent as may be required in many applications.
Unlike the catheters discussed above many of the catheters developed for use in PTA procedures utilize complex multiple balloon configurations in order to properly dilate a vessel and clear blockages. U.S. Pat. No. 4,744,366 to Jang is one such PTA catheter.
Although the Jang reference provides a catheter with a dilation region with multiple compliances, it does not provide an easy or atraumatic means to position the balloon in selected regions of the stent.
The Jang catheter uses a plurality of independently controlled balloons having the ability to be inflated over a range of pressures and diameters. As a PTA catheter, the Jang catheter is not designed to mount and deliver a stent. Even if Jang could be modified to deliver a stent, it is unclear from the disclosure if the balloons described by Jang would have the strength and puncture resistance necessary to expand and set a stent.
In order to address the problems described above and to overcome the continued shortcomings suffered by previous balloon catheters, it is an object of the present invention to provide for a medical device delivery catheter capable of inflating and setting the medical device in a vessel without a catheter or balloon exchange, while reducing the possibility of damage to the vessel by the stent or balloons.
A further object is to provide for a multiple balloon catheter capable of expanding a stent with low pressure and seating the stent into place using high pressure.
Yet another object is to provide for multiple balloon catheter capable of expanding a body lumen with low pressure and subsequently seating a medical device into the expanded body lumen using high pressure.
To achieve these and other objects, there is provided a medical device delivery catheter that has multiple inflation balloons. Preferably a catheter having two balloons, an outer balloon and an inner balloon mounted in an essentially concentric manner on the distal end of the inner tube of the catheter. The outer balloon and the inner balloon being used respectively to expand a medical device with low pressure and to then properly seat the medical device in a vessel with high pressure. The inner balloon being capable of motion inside the outer balloon on the catheter shaft. The inventive catheter may have a retractable outer sheath which surrounds the distal end of the catheter prior to delivery of the medical device.